1. Field of the Invention:
This invention relates to a nasal dispenser for atomized pharmaceutical substances.
2. Discussion of the Related Art
The use of nasally administered pharmaceutical substances is becoming increasingly more widespread. For this purpose, such substances are contained in a container or bottle, on the mouth of which there is mounted a pump or a dispensing valve with a hollow stem which when operated causes the substance to emerge through the stem cavity.
Nasal dispensers must be thin and long to enable them to be inserted through the nostrils and into the nasal cavities into which the pharmaceutical substance is to be delivered in atomized form. Such dispensers are therefore transversed by a channel of some considerable length. As the pharmaceutical substances are often very costly (for example calcitonin), the free volume of this channel must be as small as possible, so that the smallest possible quantity of substance remains trapped within it, to possibly be lost especially during the initial stage of pump operation (priming), when it is desirable for the liquid emerging from the pump stem to already fill the entire free volume of the dispenser channel on initial operation of the pump.
As dispensers are produced in large number by automatic machines, it is practically impossible to form long channels of very small cross-section. In the patent EP-B-0 131 501 it is proposed to form the dispenser channel of fairly large uniform cross-section, and then to insert into it a constant-section peg as long as the channel and having a flattened longitudinal portion on its outer surface, such as to define a small-dimension passage together with the opposing surface of the channel. This nasal dispenser has however drawbacks deriving from the fact that only a very small expansion chamber for the pressurized substance passing through the channel is provided, between the free end of the peg and the opposing wall of the dispenser where the discharge hole for the atomized substance is located, and the fact that the free end of the dispenser where this discharge hole for the atomized substance is provided has to be shaped to define a hole at and about which there is a circular recess from which tangential channels extend to impress a vortex rotary motion on the particles, which then emerge from the dispenser through the hole which, being completely free, partly reduces the desired vortex motion of the particles. As the recess and the relative tangential channels have very small dimensions and are provided within the dispenser at the bottom of the long (and fairy small) bore which traverses it, it is difficult to form them using automatic machines of high production rate without a high level of rejects.
The lack of an additional expansion chamber within the dispenser channel is a drawback because the liquid substance delivered via the stem of the pump on which the dispenser is mounted cannot be atomized to the total and complete extent which would be desirable, with consequent spraying of relatively large droplets of the substance.
This problem is well known in the state of the art, as is apparent for example from U.S. Pat. Nos. 2,775,483 and 3,471,092 which describe dispensers traversed by channels of relatively large section and housing profiled elements which define intermediate expansion chambers along the length of the dispensers between successive regions of limited cross-section for the passage of the liquid being dispensed.